Cell-cell and cell-extracellular matrix interactions allow for exchange of information between, and coordination among, various cells of a multi-cellular organism and are fundamental for most biological processes. These interactions play a role in everything from fertilization to death. Such interactions are essential during development and differentiation and are critical for the function and protection of the organism. For example, interaction between the cell and its environment is necessary to initiate and mediate tissue remodeling. Tissue remodeling may be initiated, for example, in response to many factors including physical injury, cytotoxic injury, metabolic stress or developmental stimuli. Modulation between pathology and healing (or metabolic optimization) may be done, in part, by the interaction of stimulated cells with the extracellular matrix as well as the local solvent.
The adipocyte complement related protein family plays a role in the interaction of cells with their environment, and appear to act at the interface of the extracellular matrix and the cell. These proteins include, Acrp30 (Scherer et al., J. Biol. Chem. 270:26746-49, 1995), apM1 (Maeda et al., Biochem. Biophys. Res. Comm. 221:286-9, 1996), GBP28 (Nakano et al., J. Biochem. 120:803-12, 1996), zsig39 (Sheppard and Humes, WIPO Published Patent No: WO99/10492), zsig37 (Sheppard, WIPO Published Patent No: WO99/04000), ZCRP30R1 (Smith et al., WIPO Published Patent No. WO99/56619), ACRP30R1L (Hensley et al., WIPO Published Patent No: WO99/59618), ACRP30R2 (Hensley et al., WIPO Published Patent No: WO 99/64629), PRO 353 and PRO 344 (Wood et al., WIPO Published Patent No. WO99/28462), zacrp2 (Piddington et al., WO 00/63376), zacrp3 (Piddington et al., WO 00/63377), zacrp4 (Piddington et al., WO 01/02565), zacrp5 (Piddington et al., WO 00/73444), zacrp6 (Piddington et al., WO 00/73466), zacrp11 (Piddington et al., WO 02/070704), and zacrp12 (Piddington et al., WO 02/44373).
These proteins all share a collagen-like domain comprising perfect Gly-Xaa-Pro and imperfect Gly-Xaa-Xaa collagen repeats, and a C1q domain. Complement factor C1q consists of six copies of three related polypeptides (A, B and C chains), with each polypeptide being about 225 amino acids long with a near amino-terminal collagen domain and a carboxy-terminal globular region. Six triple helical regions are formed by the collagen domains of the six A, six B and six C chains, forming a central region and six stalks. A globular head portion is formed by association of the globular carboxy terminal domain of an A, a B and a C chain. C1q is composed of six globular heads linked via six collagen-like stalks to a central fibril region. Sellar et al., Biochem. J. 274: 481-90, 1991. This configuration is often referred to as a bouquet of flowers. Acrp30 has a similar bouquet structure formed from a single type of polypeptide chain. The C1q globular domain of ACRP30 has been determined to have a 10 beta strand “jelly roll” topology (Shapiro and Scherer, Curr. Biol. 8:335-8, 1998). The structural elements such as folding topologies, conserved residues and similar trimer interfaces and intron positions are homologous to the tumor necrosis factor family suggesting a link between the TNF and C1q families.
Proteins that play a role in cellular interaction, such as transcription factors and hormones are useful diagnostic and therapeutic agents. Proteins that mediate specific interactions, such a remodeling, would be particularly useful. The present invention provides such polypeptides for these and other uses that should be apparent to those skilled in the art from the teachings herein.